It is often the case in a variety of studies of wild animals that their presence can be known by sound alone. This occurs, for example, with insects and birds whose visibility is often obscured by plant life. Another common case is with the study of cetaceans. Many species are visible at the surface for only minutes at a time, and then only under ideal sea conditions.
It is conceivable that under ideal conditions (e.g., a good source and a tuned system as described later) an individual source could be recognized by sound alone. For example, spectrum analysis via the use of Fourier Transforms could be used. Fourier transforms use the sinusoidal as a basis, wherein the purpose of performing a Fourier transform is to calculate the coefficients of a series of sinusoidal waves of different frequencies, the sum of which are a close approximation of the original signal. By knowing these coefficients one can gain an understanding of the distribution of the signal in question in what is known as “frequency space” or the “frequency domain.”
The use of Fourier analysis, however, has many limitations. For example, Fourier analysis yields a high rate of false positives and is significantly affected by noise at or near the same frequencies as the desired feature. Fourier analysis is also computationally inefficient since it utilizes a substantial amount of processing power. Accordingly, it is desirable to provide a method and apparatus for characterizing the acoustics of a particular species in order to design a system that can provide more efficient and reliable detection performance.